1. Field of the Invention
The present invention relates to a multi-shaft driving device comprising a plurality of motors for driving an articulated robotic hand or another plurality of operational shafts, and in particular relates to an apparatus for transmitting a position detection signal of a multi-shaft motor that is capable of transmitting, via a small number of wires, a detection signal from a plurality of position-detecting devices for detecting a rotation position of the motors to motor drivers for controlling the driving of the motors.
2. Description of the Related Art
A plurality of motors, e.g., servomotors, for driving operational shafts, is disposed on an articulated robotic hand or other multi-shaft driving device. A rotary encoder or other position-detecting device for detecting the rotation positions of the servomotors is attached to the servomotors. Motor drivers for controlling the driving of the servomotors control the driving of the servomotors on the basis of a position command provided from a host computer or the like, and on the basis of an actual rotation position of the servomotors that are based on a detection signal from the rotary encoders.
In such a multi-shaft driving device comprising a plurality of motors, a driving-side mechanism provided with the motors and position-detecting devices is connected via a large number of wires to the motor drivers for controlling the driving of the motors. For example, in a rotary encoder, A-phase and B-phase signals having 90° in phase difference with each other, as well as a Z signal indicating the position of an origin, are output and transmitted to a motor driver via a parallel signal transmission path. A plurality of signal wires is needed for each rotary encoder. Therefore, in a multi-shaft driving device comprising a plurality of motors, many wires extend from the rotary encoders attached to the motors, and a space for laying the wires must be maintained. In addition, when the number of wires increases, the probability of the wires disconnecting accordingly increases as well.
In JP-A 11-175118, it is proposed that the detection signal from the rotary encoders is output using a serial signal configuration in order to reduce the number of wires involved. The signal is accordingly transmitted to a motor driver via a serial signal transmission path having a fewer number of wires than is traditionally employed.